Homework Help:
Energy Dissipated by Resistor

I have the solution to this problem, but I can't figure out how to solve it for the life of me. I'd appreciate any assistance:

Image: http://www.cc.gatech.edu/~strobel/problem.gif [Broken]

The switch in the figure above has been in position 'a' for a very long time. It is suddenly flipped to position 'b' for a period of 1.25 ms, then back to 'a'. How much energy is dissipated by the 50 Ohm resistor?